Correct Answer - Option 1 : 1800

__Explanation__

Sleeper density means number of rails per rail length and it is represented by M + x ;

where 'M' is the rail length and 'x' is any integer that varies from 3 to 7.

Given:

Sleeper Density = M + 5

No of sleepers in 12.8 m rail length = 12.8 + 5 = 17.8 ≈ 18 sleepers.

So, the total number of sleepers (T) is given by

\({\rm{T}} = {\rm{}}\frac{{{\rm{Total\;rail\;length}}\; \times \;{\rm{No\;of\;sleeper\;per\;unit\;rail\;length}}}}{{{\rm{rail\;length}}}}\)

\({\bf{T}} = \frac{{1280\; \times \;18}}{{12.8}}\) = 1800